The present disclosure relates to image forming apparatuses to form an image on a sheet and particularly relates to an image forming apparatus including an optical scanning device to form an electrostatic latent image on an image carrier.
For image forming apparatuses that form an image on a sheet, optical scanning devices to form an electrostatic latent image on a photosensitive drum that carries an image have been known. In this technique, an exposure device as an optical scanning device includes, inside its housing, a laser diode, a lens, a polygon mirror, a polygon motor, an fθ lens, a steering mirror, a light transmissive member having a dust-proof function.
Laser light emitted from the laser diode is guided to the polygon mirror through the lens. Then, the light laser entering the polygon mirror that is driven and rotated by the polygon motor is reflected and deflected by the mirror surface of the polygon mirror, passes through the fθ lens, and is then reflected by the steering mirror. The laser light reflected by the steering mirror is guided to the dram surface of the photosensitive drum that is rotated in the sub scanning direction, while being scanned in the main scanning direction through the transparent light transmissive member.
For example, some exposure device further includes a shielding member that covers the light transmissive member. The shielding member is movable between a position where the light transmissive member is covered and a position where the light transmissive member is exposed. In the case where an image forming apparatus has an openable outer cover, covering the light transmissive member with the shielding member can prevent the laser light from being emitted outside the image forming apparatus. Further, in the aforementioned exposure device, a cleaning member capable of cleaning the light transmissive member is mounted at the shielding member. When the shielding member moves to the position where the light transmissive member is covered, the cleaning member comes into contact with the light transmissive member, thereby removing toner and dust adhering to the light transmissive member.